The present invention generally relates to papermaking machines and more specifically concerns a new and improved construction of a pressing or press section for use in a papermaking machine for the dewatering of a paper web or the like.
Generally speaking, the pressing or press section of the present invention is of the type comprising two separate or spaced pressing locations arranged in tandem or succession. Each pressing location comprises an upper pressing surface and a lower pressing surface which define an extended or wide nip therebetween. The paper web to be dewatered is guided between an upper felt belt and a lower felt belt.
It is known to the art, for example, from German Pat. No. 3,328,162, published Feb. 20, 1986, that high-speed papermaking machines require a closed or sandwiched guidance of the paper web up to the drying section of the papermaking machine. The paper web is thus located between an upper felt belt and a lower felt belt and guided therebetween through pressing locations arranged in tandem or in series in the direction of travel of the paper web during linear or straight web guidance.
However, this positive web guidance has the disadvantage that, each time after leaving the respective pressing location, the paper web is re-wet with liquid or moisture which has been previously transferred into the felt belts in that the paper web sucks back such liquid or moisture. This is particularly undesired in the case of so-called extended nip presses, in the extended or long or wide nip of which the rate of dewatering is especially high during the prolonged web residence time in such an extended nip.